To design an amplifier stage, a
source and load impedance combination must be found that gives
the gain desired. Synthesis can be
accomplished in three stages.
Step 1
The vector voltmeter measures
the scattering parameters over the
frequency range desired.
Step 2
Transducer power gain is
plotted versus frequency using
equation 19 and the measured data
from step 1. This determines the
frequency response of the uncompensated transistor network so that
a constant-gain amplifier can be
designed.
Step 3
Source and load impedances must
be selected to provide the proper
compensation of a constant power
gain from 100 to 500 Mhz. Such
a constant-gain amplifier is de-
signed according to the following:
â¢ Plot SnÂ° on the Smith chart.
The magnitude of Sn* is the linear
distance measured from the center
of the Smith chart. Radius from
the center of the chart to any point
on the locus of Sn represents a
reflection coefficient r. The value of
r can therefore be determined at
any frequency by drawing a line
from the origin of the chart to
a value of su* at the frequency of
Step3
-lOOMhz^ONSTANT
â SOOMhz | CIRCLES
J *M
Source impedance is found by inspecting the input plane for realizable source loci that give proper gain. Phase
angle is read on the peripheral scale "angle of reflection coefficient in degrees."
Electronics | September 5, 1966